Abstract: A method for judging effectiveness of a drug having protease inhibitory activity, which comprises the steps of: (1) bringing a biosample isolated or collected from a patient with a disease in which participation of a protease is suspected into contact with a thin membrane containing a protease substrate and formed on a surface of a support; (2) detecting a trace of digestion formed on the thin membrane by action of a protease; and (3) judging that a drug having protease inhibitory activity is effective for the patient when a trace of digestion is formed on the thin membrane. The method enables accurate judgment as to whether or not a drug having protease inhibitory activity is effective for a patient with a disease in which participation of a protease is suspected such as rheumatoid arthritis and cancer before administration of the drug.